System And Method For Controlling An Anode Side Recirculation Pump In A Fuel Cell System - Patent 8129056 by Patents-31

1. Field of the Invention This invention relates generally to a method for controlling the speed of a recirculation pump in an anode recirculation loop of a fuel cell system and, more particularly, to a method for controlling the speed of a recirculation pump in an anoderecirculation loop of a fuel cell system to provide the proper ratio of fresh hydrogen to recirculated anode gas, where the method includes using a mathematical model based on system parameters. 2. Discussion of the Related Art Hydrogen is a very attractive fuel because it is clean and can be used to efficiently produce electricity in a fuel cell. A hydrogen fuel cell is an electrochemical device that includes an anode and a cathode with an electrolyte therebetween. The anode receives hydrogen gas and the cathode receives oxygen or air. The hydrogen gas is dissociated in the anode to generate free protons and electrons. The protons pass through the electrolyte to the cathode. The protons react with the oxygen andthe electrons in the cathode to generate water. The electrons from the anode cannot pass through the electrolyte, and thus are directed through a load to perform work before being sent to the cathode. Proton exchange membrane fuel cells (PEMFC) are a popular fuel cell for vehicles. The PEMFC generally includes a solid polymer electrolyte proton conducting membrane, such as a perfluorosulfonic acid membrane. The anode and cathode typicallyinclude finely divided catalytic particles, usually platinum (Pt), supported on carbon particles and mixed with an ionomer. The catalytic mixture is deposited on opposing sides of the membrane. The combination of the anode catalytic mixture, thecathode catalytic mixture and the membrane define a membrane electrode assembly (MEA). MEAs are relatively expensive to manufacture and require certain conditions for effective operation. Several fuel cells are typically combined in a fuel cell stack to generate the desired power. For example, a typical f